This is a somewhat unusual source post, as I don’t think any of the material here can be used directly for Art Song Central.
Nevertheless, Germany’s Brahms Institute has put what appears to be the complete works of Johannes Brahms in original editions on their website:
They appear to be in high enough resolution to print legibly, but prints will still be a bit blurry and all pages are served with a Brahms Institute watermark.
Still, even if less than ideal for use in performance, this is a wonderful resource for them to make available!
Update: Many of these scores have been “harvested” by IMSLP and are available in PDF form via their page of Brahms Lieder, which should make them a bit easier to download and print.