Glider pilot reported another aircraft on climb out from crossing runway passed below; resulted in taking evasive action and a NMAC event.

Narrative

While flying an instructional flight glider traffic reported the initial reporting point to Truckee Tower requesting to land on Runway 02 (The typical runway for landing gliders at Truckee is Runway 20; holding short of Runway 29-11 upon landing). Tower approved landing on Runway 02 and gave permission to land. The glider had the intention of flying an approach such that we touched down after the intersection. Truckee is known for sink and turbulent conditions in the pattern causing gliders to approach closer and higher than typical glider operations. The glider turned downwind roughly over the numbers Runway 29 as Truckee Tower approved Aircraft Y to take off on Runway 29. Shortly after the glider turned base as necessitated by the altitude the glider had to make a safe landing. A few seconds after the glider started turning base the Tower requested that the glider turn base further out (not knowing we had already turned base). The Tower then realized immediately that the glider had already turned base and requested that the Aircraft Y abort the take off. The Aircraft Y continued its roll and took-off underneath the glider as we turned final; again necessitated by our altitude (gliders cannot go-around). The Aircraft Y did not respond to towers request to abort and continued its climb as the glider performed evasive maneuvers to position itself behind and on above of the Aircraft Y before lining up with the runway and performing a safe touchdown after the intersection.