- I'd love to see each license that has a standard SPDX identifier (https://spdx.org/licenses/) include that identifier as metadata in its tldrlegal record. (And ideally tldrlegal.com should have a standard URL to reach the one-and-only license corresponding to a given SPDX identifier.)
- I'd love to see standardized tags for OSI-compliant Open Source licenses, GNU-approved Free Software licenses, GPLv2-compatible licenses, and GPLv3-compatible licenses. (For the latter two, it'd be interesting to have a generalized tagging mechanism for saying "compatible with (other license record)", but in practice those are the two cases that matter most, and too much generality might not be a good thing.)
Also, this site seems to be doing something with icon fonts that doesn't work: I see missing-character glyphs for characters F098 and F099 where Facebook and Twitter icons should appear, and an "fl" ligature where a search button should appear. (Firefox 27 on Linux, in case that matters.)
I also don't see the placeholders on the username, email, and password fields in the form that pops up when clicking the "Sign Up" link; the placeholders in the form on the front page do appear. (Consider using real labels rather than placeholders for forms like that, to make them more accessible.)