Quote from JayF_eSignal:
eSignal's API is intended for commerical use only, however with the release of 7.4 will come support for ActiveX. ActiveX is a development tool adopted by eSignal to give third party users, including brokers, software developers and individual users, access to quotes, tick and history data, trading information and more. The ActiveX tools provides third party with the ability to access eSignal data through the eSignal application and Data Manager.
ActiveX permits third party to develop an application in any language. Only a few lines of code are required for developing applications that receive quote data and only slightly more development is required for accessing tick and history data. In addition to developing third party applications that use quote and history data, ActiveX can also be used to send data to a trading ticket for order execution and for receive trading information back into eSignal.
Further details regarding pricing will be provided once 7.4 is released.