After some confusion among the moderators, we have decided to reinstate the source link requirement for gifs - any gif posted will once again require a source in the comments or be removed (and reapproved if the OP replies with a source).
Further - there are some rules updates regarding source links, since bot and poweruser accounts posting bad sources seem to be the newest trend among spammers:
Source links are subject to the same rules on URLs as link submissions - meaning that less reputable sites are only allowed if they are the sole easily locateable source of the gif. Posting something like a pornhub video embedded on a shitty site rather than linking the pornhub video directly will result in a warning and potential ban.
Posting an obviously false source as the OP will result in a ban, or a warning if it is plausibly an honest mistake.
After seeing some original content in gif form and some discussion with users, I've decided to amend rule 7 to add an exemption for original content.
From this point forwards, sourceless gifs will be allowed if and only if they are your original content (i.e you are either filming or in the gif) and the source video is not published anywhere (including paywalled sites).
Edit - if you are submitting a gif under this exception, it should be clearly marked as OC.