I was going to install lazarus-project_2.0.8-0_amd64.deb on my Xubuntu and I've seen that Software (the application that installs it) says the license is private (Actually "Privativa" in Spanish, don't know how's in English).
Thats because you are looking at it using the Gnome supplied 'Software' or 'Software Install' tool. It classes anything that does not come from its own repository as proprietary. I have seen numerous bug reports on the topic, they just seem to be ignored and, quietly closed. I suggest you install gdebi and use that instead.
As an experiment, grab a deb from your /var/cache/apt/archive/*, to be really nasty, see if you can find gnome-software..... It most certainly came from the approved repository and is open source. Open it with Software-Install and you will see it claims it, itself, is proprietary !
Any file that is not in the official repository is reported as proprietary. Even if it came from the repo.
I believe newer distros have stopped that particular tool from claiming its a general software management tool. Gdebi is your friend.
Davo