In the end of 2004 in Lithuania first big e-government projects financed by EU structural funds should start, and developing and implementation of software will constitute an integral part of these projects. Before starting the projects it must be determined how new and current information systems should be integrated and their interoperability ensured. Usage of commercial software system will lead to attachment to the sole producer, it will reduce competition and will deprive from choosing other software providers. Alternative solution would be to develop open source (OS) systems and as a consequence create better competition for the development of such systems. This work intends to analyze solutions for information system integration and interoperability through using open source software, open standards and their implementation for e-government services. Open source software and open standards are analyzed and major features defined to estimate their advantages for the usage at government institutions. Modern information system integration methods and open source realization possibilities overlooked. Lithuanian and foreign legislation on open source are reviewed. From research materials the analysis is given about the usage of the open source software, open standards at the governmental institutions, determining factors for the usage and opinion of institutions. As the review shows at the present time open source and commercial software have unequal positions with the... [to full text]