D iversity is a defining characteristic of global collectives facilitated by the Internet. Though substantial evidence suggests that diversity has profound implications for a variety of outcomes including performance, member engagement, and withdrawal behavior, the effects of diversity have been predominantly investigated in the context of organizational workgroups or virtual teams. We use a diversity lens to study the success of nontraditional virtual work groups exemplified by open source software (OSS) projects. Building on the diversity literature, we propose that three types of diversity (separation, variety, and disparity) influence two critical outcomes for OSS projects: community engagement and market success. We draw on the OSS literature to further suggest that the effects of diversity on market success are moderated by the application development stage. We instantiate the operational definitions of three forms of diversity to the unique context of open source projects. Using archival data from 357 projects hosted on SourceForge, we find that disparity diversity, reflecting variation in participants' contribution-based reputation, is positively associated with success. The impact of separation diversity, conceptualized as culture and measured as diversity in the spoken language and country of participants, has a negative impact on community engagement but an unexpected positive effect on market success. Variety diversity, reflected in dispersion in project participant roles, positively influences community engagement and market success. The impact of diversity on market success is conditional on the development stage of the project. We discuss how the study's findings advance the literature on antecedents of OSS success, expand our theoretical understanding of diversity, and present the practical implications of the results for managers of distributed collectives.

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This paper examines the factors that influence the long-term sustainability of FLOSS projects. A model of project sustainability based on organizational ecology is developed and tested empirically. Data about activity and contribution patterns over the course of five years for 2,772 projects registered with SourceForge is analyzed. Our results suggest that the size of the project's development base, project age and the size of niche occupied by the project are positively related to the project's ability to attract user and/or developer resources. The ability to attract resources is an indicator of the perceived project legitimacy, which in turn is a strong predictor of the project's future sustainability. Thus a project's ability to attract developer and user resources is shown to play a mediating role between the demographic (size and age) and ecological (niche) characteristics of the project and its future sustainability. Our results support the applicability of tenets of organizational ecology related to the liability of smallness, the liability of newness, and population characteristics (niche size) to the FLOSS development environment. The implications of the results for future research and practice are discussed.

In a thermodynamic system, a stable phase diagram is uniquely determined by the thermodynamic parameters of each phase. A generalized phase equilibria calculation software package should enable the calculation of the phase diagram from the parameters automatically, without requiring either prior knowledge of the diagram or special user skills. Improvements to the existing software packages have been achieved in the new software package PANDAT. The approach used in this software is described briefly and some examples of its advantages are given.to the thermodynamic parameters of phases and the con-

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