I think there are two possible concerns: 1.) The interest of their clients and the larger community may not align or even directly contradict each other. For e

I think there are two possible concerns: 1.) The interest of their clients and the larger community may not align or even directly contradict each other. For example, it has been argued that the consulting work of the OpenSSL developers has been detrimental to the quality of the software and that it may have been one factor leading to the recent security problems. 2.) The Julia developers may at some point decide not to publish future additions to Julia under an open source license. Instead they may decide to sell an "enterprise" version of Julia. I don't know how likely these things are but there is certainly plenty of precedent in the open source world showing that it's possible.