modeltech(modelsim) for linux platform, license?

i want to learn about vhdl, but i can't get modelsim's evaluator license..

how can i get it?

i already have modelsim for windows platform, and

i have modeltech(sim) for linux..but i can't run, use it...

because i have no license... how can i get it?

i want free license..(for student...)

any idea? help me... i want to learn vhdl....

ParkSungJae