li.ppy.sh, more commonly known as pTransl, was a community-based localisation platform run and hosted by peppy. It was primarily used to enable members of the osu! community to localise the game into their own languages.
pTransl was launched in July 2009 and functioned similarly to that of localisation platforms such as Crowdin. Upon registering, users could suggest translations of the game's strings into their native language or vote on existing suggestions from other users.
Suggestions were approved or denied into the game based on their vote count. Upon accumulating three positive upvotes, suggestions were considered to be "approved by the community" and subject to be added to the client's localisation files in the next update. Similarly, suggestions with three negative downvotes were considered to be "denied" and would be hidden from the list of suggested translations.1
Following the successful use of Google Docs for the localisation of osu!stream, pTransl was decommissioned in November 2012 to avoid redundancy as community localisation efforts were shifted over to the new service.2
Forum thread by peppy (2009-07-27): "pTransl - community translation" ↑
Forum thread by peppy (2012-11-04): "osu! Community Localisation Project" ↑