Sage One is described as 'Nothing should get in the way of building your dream business. Least of all complexity. Sage One is online accounting software that makes quick work of the daily tasks you know you need to get right. No accounting experience required' and is an app in the Business & Commerce category. There are more than 25 alternatives to Sage One for a variety of platforms, including Online / Web-based, Windows, Mac, Linux and iPhone. The best alternative is Odoo, which is both free and Open Source. Other great apps like Sage One are ERPNext (Free, Open Source), inoERP (Free, Open Source), Tryton (Free, Open Source) and insightly (Freemium).
Odoo (formerly OpenERP) is a suite of open-source business apps written in Python and distributed under the AGPL license, under the Open Core software business model. It is used by 2 million users worldwide to manage companies of all size.
ERPNext is a free and open-source integrated Enterprise Resource Planning (ERP) software developed by Frappé Technologies Pvt. Ltd. and is built on MariaDB database system using a Python based server-side framework.
inoERP is an open source php based enterprise management system. The ERP systems contain all the required modules for running any small to mid-size businesses. The features are very similar to Oracle R12/ Fusion Application and SAP.
Tryton is a three-tiers high-level general purpose application platform under the license GPL-3 written in Python and uses PostgreSQL as database engine. It's the core base of a business solution providing modularity, scalability and security.
webERP is a complete web based accounting/ERP system that requires only a web-browser and pdf reader to use. It has a wide range of features suitable for many businesses particularly distributed businesses in wholesale and distribution.