He had no other choice. However, when Harry Potter tricks Lucius into giving Dobby something with a sock hidden in it, Dobby is suddenly freed, and he was allowed to do anything he wants from that ...

he helped Dobby become a free elf by tricking Lucius into giving Dobby a sock. Giving clothes to a House-elf was the only way to free them, which Harry knew. And since then, Dobby became eternally ...