I was wondering if anyone as experience with sites selling copies of movies or music with similar policy to gog.com.
In other words: no DRM, no software you have to download, unlimited download and redownload, easy registration... And of course _lawful_.

Do you know any? What is your experience?

There aren't great stores like GOG for those, but you can check some suggestions from users here in my thread:
digital_stores_like_gog_for_other_media

Bit hard, because unlike video games there is delivery charge and the royalties, publishing, merchant fees, etc. and it will be more complicated if it is for live concert.

I've good experience with bandcamp, but they doesn't offer unlimited download. I also bought a live Metallica show hosted by nugs.net. The soundboard quality is excellent, the files are sorted complete with their tags for easy access in mobile devices. Unfortunately the download is only for one-time only, and must be completed within 48 hours. They won't entertain request for additional download.

I buy tons of music from Amazon, no DRM on the Audio files. I dont know a single option for movies.