PLCopen — Bridging PLC, Motion Control, and Robotics

One of the main ways of selling PLCs at present is locking in clients to your brand by having a unique language that the client's engineers are forced to "learn" with the initial project. For a new open source language to be successful you need to get 2 or 3 of the largest players on board. There is no incentive for them to support a language that allows the next project to go to one of their rivals. Linux is the best example of the degree of penetration that is achievable by a comparable open source language without corporate backing.

The "learn" is in inverted comma's because in my experience (UK) few end users train their staff adequately to maintain in house equipment. Brand loyalty is more often associated with a reduction in spares inventory.