# Open-Source Software Development in Cheminformatics: A Qualitative Analysis of Rationales
## 1 Introduction  
Cheminformatics has been used in chemistry research since the field adopted computers in the 1940s [1]. Depending on the perspective, the first cheminformatics paper was published in 1946 by [PERSON] et al. [2] or in 1957 by [PERSON] and [PERSON] [3]. According to [PERSON] [1], [PERSON] et al. [2] may be the first scholars who applied computers in chemistry research. However, according to [PERSON] [4], the first actual cheminformatics paper was published in 1957 [3], where [PERSON] and [PERSON] described an algorithm for substructure searching. [PERSON] [4] argues that the importance of this article was its application of graph theory in searching and visualizing chemical structures. The algorithms have been significantly developed over the decades, but applying graph theory has been the foundation of major cheminformatics applications such as structure searching and registration, substructure searching, and similarity searching [4]. These applications are still the key techniques used in four traditional cheminformatics research areas, which are (1) chemical databases, (2) computer-assisted structure elucidation systems, (3) computer-assisted synthesis design systems, and (4) modeling and visualization tools [1]. On a practical level, cheminformatics scholars are developing methods, for example, to search large databases efficiently or model physical, chemical, and biological properties of molecules for predictive purposes [4]. Although cheminformatics as a field has been around for many decades, it has developed to a recognized and independent sub-discipline of chemistry only in recent decades [4; 5]. Many scholars find this strange, as computers are widely used in chemistry and it has even been speculated that most novel chemistry entities in the future will be discovered in silico [6]. One reason is that much of the cheminformatics research has been conducted in industrial laboratories, not academia. Because of this, many applications and methods are not published due to intellectual-property-rights issues [4]. In this regard, the key solution for developing the field is to support free and open-source software (FOSS), which removes all limitations on users or applications [7]. This also includes industrial applications, which are a major component in the field of cheminformatics [4]. The potential of open-source development in cheminformatics has been recognized decades ago. There are multiple articles that describe the benefits of open source. For example, [PERSON] et al. [8] emphasized the importance of open-source resources in supporting the needs of the pharmaceutical industry by connecting chemistry and computer sciences via cheminformational thinking. [PERSON] [9] wrote that open source and open data should be a standard in chemical research. It would enable reproducibility which supports scientific reliability. Open source code would also lower the research costs significantly. Derived from the described background, this article aims to promote open cheminformatics by exploring the rationales set for open-source projects declared as cheminformatics software development in the research literature. We argue that the topic is important because software development is one of the most active research areas in cheminformatics [1]. Even though the field produces a great deal of new software, according to our knowledge, there is no earlier research that has explored open-source software development in cheminformatics in a larger scale. Open source is especially important considering the hindrance that the industrial background has caused for the development of open cheminformatics [4]. A recent review revealed that cheminformatics research strongly emphasizes software, databases, and web applications developed for data analysis. This trend is likely continuing because of the current highly active research topics, such as machine learning, which demand up-to-date technological solutions [5].