The Ludum Dare version is older, with unfixed bugs and without the proper boss at the end. If you're not playing specifically to rate the Ludum Dare version then we recommend you download the latest.
Recent community posts
A custom solution would be simple to implement. We just need a textfield to take submissions. If it's done like ludum Dare, then the next while is "theme slaughtering" which is also a simple system. Pick a random theme from the database, give the user the option to vote up or down.
After that, voting rounds begin by picking the top 100 or so, dividing them in to groups of 20, and making one group available per week.
This whole system could be completely automated, down to entering a handful of dates (start date, voting length, number of rounds, etc) and then releasing the theme at the start time.