Open Source
Taler Bullion centers around open source software.
The entire toolchain of Taler Bullion is based on open source software. Furthermore, it is made available at no expense. This is possible thanks to donations from institutions such as NLnet.
Open source software is the way to make software accessible to everyone, without fee or license, except for an obligation to share equally in case any changes are used. This last bit ensures that there can be free and open competition on business grounds, with maximum reuse of lessons learnt.
Taler Bullion as a whole benefits from such openness. It allows a fast pace of development, with maximum reuse and so, with minimal costs for the software that makes it happen.