Stealing an open source project would be like saying stealing quick sort. You can't steal something if it was given to the public domain.
"Grant of Copyright License. Subject to the terms and conditions of this License, each Contributor hereby grants to You a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare Derivative Works of, publicly display, publicly perform, sublicense, and distribute the Work and such Derivative Works in Source or Object form."
Most open source projects are not given to the public domain, but encumbered with clauses in the form of their license.