This time last year, I was researching and writing our CAOS report, ‘Mobility Matters.’ At the time, we indicated that open source software was prevalent across all layers of the mobile software stack. We viewed Linux and its various mobile forms — Android, Moblin, Ubuntu Netbook Remix and others — as a weapon that OEMs would wield competitively, particularly as they responded to Apple and its deep iPhone disruption. However, we also noted that open source tends to be actually less open in the mobile world. Developments this week and ongoing indicate this continues to be the case.

We wrote last year about how openness was emerging as a significant factor, differentiator and disruptor in the mobile software market, with Apple enjoying success with its closed, controlled approached, but also getting pressure from more open plays, such as Google’s Android.

Now we see it is Android that is feeling the pressure. I believe new and different players, as well as venerable mobile vendors, all have tremendous opportunity around Linux and open source software in mobile and consumer devices. However, the more strings, NDAs, licenses and developer agreements they add, the more they close development, the process and applications, the more they curtail the opportunity.

We can understand and appreciate the need for carriers and handset makers to control certain aspects of how a mobile device behaves, communicates and interfaces with the user. However, on the other end of the line, where we have ISVs, software developers and other members of this market and community, real openness and transparency is critical. Here, the hooks and controls don’t make as much sense and, frankly, don’t cut it with developers.

While this is not the first time I’ve questioned Google’s approach and Matt has illustrated the problem with half-open, I do believe it is among the key stakeholders in the open mobile opportunity. Still, it is now being put to the test and will have to respond appropriately if it is to retain widespread respect among developers. And Google and Apple are not alone. Any vendor that is picking its fruit from the open source tree must be wary of the line between being open and not.