Since FLAC is an open-source project, it's important to have a set of goals that everyone works to. They may change slightly from time to time but they're a good guideline. Changes should be in line with the goals and should not attempt to embrace any of the anti-goals!

Goals

• FLAC should be and stay an open format. The source code is all either LGPL'd or GPL'd.
• FLAC should be lossless. This seems obvious but lossy compression seems to creep into every audio codec. This goal also means that flac should stay archival quality and be truly lossless for all input. Testing of releases should be thorough.
• FLAC should yield respectable compression, on par or better than other lossless codecs.
• FLAC should allow at least realtime decoding on even modest hardware.
• FLAC should support fast sample-accurate seeking.
• FLAC should allow gapless playback of consecutive streams. This follows from the lossless goal.
• The FLAC project owes a lot to the many people who have advanced the audio compression field so freely, and aims also to contribute through the open-source development of new ideas.

Anti-goals

• Lossy compression. There are already many suitable lossy format (Ogg Vorbis, MP3, etc.).
• Copy protection of any kind. Don't get me started, just see the features page for the short answer.