SOURCES.md: clarify YCB-Sight uses the original GelSight sensor (not Mini) — primary reason for exclusion, with viral-copyleft license as secondary

SOURCES.md

@@ -624,8 +624,7 @@ real-world objects) in the entire dataset.
   frames before noticing the channel-signature mismatch and verifying
   against the paper. Removed from this aggregate; could go to a
   separate "gelsight-large-pretrain" repo if needed.
-- **YCB-Sight** — CC-BY-SA-4.0 (viral copyleft), and the sim is not
-  Mini-calibrated. Not included.
+- **YCB-Sight** — uses the **original (larger) GelSight sensor**, not the Mini, so the gel surface and illumination geometry differ. Also CC-BY-SA-4.0 (viral copyleft) and the sim is not Mini-calibrated. Not included.
 - **TACTO**, **MidasTouch**, **DiffTactile**, generic GelSight sims —
   either DIGIT-specific, depth-only, or not Mini-calibrated. Not
   included.