And I never did anything in C or C++ before so that's a challenge....

Also, FreeBSD switched to a different packaging system so I can only help with the new one.. The older version might still be used on older FreeBSD versions but I can't test that..
It's a different command so it shouldn't be a problem.

Do you think you can split this topic? The software stuff for FreeBSD is an entirely different topic....

Support for System.InstalledProducts: it would speed things up if you can provide command(s) for querying list of installed packages.
Right we have following columns in the table (some of them can be empty, of course): NAME, VERSION, VENDOR, DATE, URL, DESCRIPTION

Another option – you can try to add it yourself, it's quite easy (check function H_InstalledProducts in Linux subagent):
http://git.netxms.org/public/netxms.git/blob/refs/heads/develop:/src/agent/subagents/linux/packages.cpp?js=1#l26 (actual code)
http://git.netxms.org/public/netxms.git/blob/refs/heads/develop:/src/agent/subagents/linux/linux.cpp?js=1#l485 (table registration)

I'll try to hold my breath for it to end up in 2.0

(Btw, the reason I wanted to use it is because listing installed software doesn't work on my FreeBSD system..
Is it worth opening a new support thread for this or is this simply unsupported at the moment?)

Tables are fully supported by the agent ("FileSystem.Volumes", "System.InstalledProducts", "System.Processes", etc.).
However, as you correctly noted – table can't be configured as external parameter at the moment (only ExternalParameter, ExternalParameterProvider, and ExternalList).
This is on our TODO list, and hopefully it will make into 2.0 release.