Freeware and Open Source packages
The distinction between "Freeware" and "Open Source" is based on politics, licensing and interpretation. For this discussion, there is no distinction. It simply refers to "Software that is available, both as a "finished" product as "source code", and developed without commercial goal".
"Freeware" and "Open Source", are two of those forgotten heritages of the Digital PDP area, when a lot of programs have been developed to run in any of the PDP-environments - and there were a few of them. These developments were shared between PDP users, including code, for the cost of media - tape, in those days. A matter of behaviour and trust: you don't make money with something someone else has put an effort in, without paying tribute.
One major source for Digital-based software was DECUS - the DEC User Society. Originally, members would write the manuals that Digital didn't deliver with their great products. These developers were technicians, not technical writers. But soon members start sharing what they developed for their normal work, and you would only pay for the media - tape, in those days. That's why even today, where the Internet is the basic media for transferring the files, the archives of Encompass are still referenced to as the DECUS tapes).
You could trust your co-members, not to use your software in their own, unless you explicitly agreed (and were paid). Most software carried a header that stated it as your product, but you could also void any right explicitly.
Sometimes, there is a reason the formalize rights-of-ownership, like the MIT and Berkeley-style licenses: The university OWNS the software and idea, but you are free to use it in your software. Others adhere to a fully free source community, like the GPL licenses, that sort of disallows local copies of the software. Yet another form is the Apache-style license, that allow you to embed the software into your product, as long as the source code is available.
Packages for OpenVMS may contain anything from a single program to a whole suite of software and related files. It spreads to a single, helpful program you can use in everyday work, to the complete set of files used to run a service, or business program. Some come from HP/Compaq/Digital, some come from The Community: VMS users that publish the programs they use for their work, so others may have that benefit as well. Some are VMS native from the start, some have been ported from other platforms - mainly Unix/Linux.
Apart from programs, there are a number of 'layers' available that should hide platform specifics and allow programs to run in any environment. These programs should therefore also run on OpenVMS - at least, that's the omission.
Like PHP, Perl and Python. You can find a lot of usable freeware packages. Be aware though that the PHP and Perl engines on OpenVMS are not the latest ones. The PHP engine is based on PHP version 5.2 (as delivered in the MOD_PHP package - which isn't complete), and Perl is based on 5.6. Latest versions ín the wild' are 5.2 - more complete - and 5.10, on the moment of writing. Python however is well up to date, and comes with some nice frameworks and applications - like this wiki 
And of course, there is a database. MySQL has been ported to OpenVMS some time ago, versions 4.1 and 5.1 are available - I strongly recommend 5.1 because of the vast increment in stablity.
Native OpenVMS software
There are quite a number of system management tools and services that have been developed on OpenVMS with, of course, OpenVMS in mind. It causes these programs to run out-of-the-box, without particular configuration; you use VMS syntax for any file specification, and all ususal RMS file formats are supported. And because of it's origin, software will be cluster aware - without anything specific.
Some of these packages have their origin in the PDP area and have been ported to OpenVMS. In the VAX days, a lot of tools have been developed for VMS on VAX since it was very specific and different from what RSX-M and RSTS-E users were used to. When Alpha was introduced in 1992, some of these packages were ported to that new hardware platform, others were re-written from the ground up. A similar movement will take place in the transition to Itanium.
The freeware site at HP contains abstracts of, and ZIP files of the 4.0 to 8.0 CD's, but offers no access to the contents of the CD. Although they offer other locations where the software used to be accesaable, I found ,ost links, but the last (which is an FTP site) no longer existing. Nevertheless, you can still get to the content from here. It's a plain copy of the CD contents, and I just added a file per CD showing what's on it.
Older software, once supplied, can probably still be found in the archives.
Another source, containing most, if not all, software ever created for DEC/Compaq/HP equipment once was located at SAIC, but that location is now closed. All it's contents - ranging from the original DECUS Tapes (including PDP (RSX, RSM) code) up to the latest (V8) Freeware CD - is now found at the DECUS Library Compendium
Most software on the Process Software File server is VMS-native as well. Most software on this site has to do with system management and services, some help you on system development.
The WASD web server is a native OpenVMS web server comes with a number of tools and facilities. So does the OSU (Ohio State University) web server. But where the WASD server comes as bouth source and object files, only needing a LINK, the OSU server kit consists of sources only and you'll need the VMS C-compiler got get it build.