Well, Reaper works with FLAC as if it were WAV... And it's small so everyone can download it and use within the trial time. And even after that, as it's uncrippled.
And, even so, your DAW doesn't have to support FLAC. There are audio converters out there (myself uses AIMP audio player, it comes with audio converter as well). FLAC transforms to WAV 1:1. So you can download the FLACs, convert to WAV, work in your DAW, export to WAV, convert to FLAC, upload. A bit convoluted, but you do end up with a lot smaller file for upload/download.