A bit of teenage angst is cropping up in speculation about acquisitions of open source software companies. With the $500 million buy of XenSource by Citrix Systems Inc. and previous buys by RedHat Inc. and Oracle Corp. last year, open source software providers have become viable targets despite worries about lack of sales and compromised code that could lead to legal disputes. But the youthful idealism that prompted the formation of these firms is facing something of a test.