We previously posted the Sigrok open source logic analyzer client. They’ve done a lot of work and it now supports the Saleae Logic, EE Electronics XLA/ESLA100, and ASIX SIGMA. Open Logic Sniffer support is in progress, which will enable Bus Pirate support at the same time.
The Logic Sniffer is $45, including worldwide shipping. The Bus Pirate is available at Seeed Studio and Adafruit Industries.